Herbicides are very important chemicals for labor-saving of weed control and improving the productivity of agricultural and horticultural crops. Herbicides have been therefore actively studied and developed for many years, and a variety of herbicides are practically used. However, it is still desired today to develop novel chemicals having further prominent herbicidal properties, particularly chemicals which can selectively control target weeds alone without causing phytotoxicity on cultivated crops and which can also control them at a low dosage.
During a planting time of corn, etc., triazine-based herbicides such as atrazine and acid anilide-based herbicides such as alachlor and metolachlor have been conventionally used. However, atrazine shows low efficacy to gramineous weeds, and on the other hand, alachlor and metolachlor show low efficacy to broad-leaved weeds. It is therefore difficult at present to control gramineous weeds and broad-leaved weeds together simultaneously with a single herbicide. Further, the above herbicides are undesirable in view of an environmental problem due to their high dosage requirement.
In view of the above circumstances, the present inventors have invented novel triketone derivatives having a thiochroman ring and filed a patent application therefor (International Patent Application WO94/04524). A typical example disclosed in this Publication is as follows. ##STR3##
However, the above compound is not fully satisfactory in soil treatment activity although it is free of phytotoxicity on corn and has high foliar treatment activity.